STATISTICAL TECHNIQUES AND TOOLS
CONFIDENCE INTERVALS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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(146.54, 164.52)
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(147.57, 163.48)
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(147.59, 163.46)
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(143.69, 167.36)
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Detailed explanation-1: -Solution: To find the sample size, we need to find the z-score for the 90% confidence interval. This means that we need to find the z-score so that the entire area to the left of z is 0.90+1−0.902=0.95 0.90 + 1 − 0.90 2 = 0.95 . So z=1.6.
Detailed explanation-2: -Find the minimum sample size required to estimate the proportion to within three percentage points, at 90% confidence. Solution: Confidence level 90% means that =1−0.90=0.10 so ∕2=0.05.
Detailed explanation-3: -A smaller sample size or a higher variability will result in a wider confidence interval with a larger margin of error. The level of confidence also affects the interval width. If you want a higher level of confidence, that interval will not be as tight. A tight interval at 95% or higher confidence is ideal.